The present invention relates generally to a semiconductor memory device and a method of operating the same.
High density memory has been continuously required since manufacturing techniques for semiconductors have improved. A memory device having three-dimensional structure, where memory cells are vertically stacked on a silicon substrate, has been suggested, since a memory device having two-dimensional structure, where the memory cells are formed with one layer on the silicon substrate is reaching a limit.
However, a problem exists in that a process for three-dimensional structures is unstable and/or the reliability of the memory device has deteriorated in the new three-dimensional structure. Various methods for solving the problem have been suggested.
For example, in the memory device having three-dimensional structure, one bit line is connected to plural cell strings. Accordingly, a problem exists in that the number of times a pass voltage is applied to each word line increases every time a program operation is performed, causing the threshold voltage of the memory cell to change based on the pass voltage.